1. Technical Field
The present disclosure relates to a detection calibration circuit that calibrates the power of a transmission signal and a transmission apparatus.
2. Description of the Related Art
In recent years, for wireless communication with high-speed transmission, a high-frequency band (for example, a frequency band of some hundreds MHz such as a millimeter wave band) is used in one channel to secure the band of a modulation signal and perform higher-speed transmission. Furthermore, for wireless communication with high-speed transmission over a long distance, the signal level needs to be maintained constant between a transmission apparatus and a reception apparatus to stably maintain the quality of the high-speed communication.
In the transmission apparatus, a power control circuit that detects power by using a detection circuit and adjusts a gain of an amplification circuit is used so that the power of a transmission signal is maintained constant regardless of an external perturbations (for example, a temperature fluctuation and a power supply fluctuation). For example, because the gain characteristic of a transistor used in a detection circuit is insufficient in a high frequency region such as a millimeter wave band, fluctuations in the gain characteristic due to the temperature, the power source, and aging are increased. Therefore, in the detection circuit, variations in the input-output characteristic are increased, whereby an error is generated in the output voltage of the detection circuit (hereinafter, referred to as “detected output voltage”).
Furthermore, because the input control range of the detection circuit is narrow in a high-frequency band, when variations in the input-output characteristic of the detection circuit are great, the input voltage level of a high frequency signal to be input deviates from the input signal range and the detected output voltage becomes inaccurate.
As a related art for reducing variations in an input-output characteristic of a detection circuit, a transmission power control circuit described in Japanese Patent No. 4304296 is proposed, for example. Furthermore, as a related art for suppressing variations in an input-output characteristic of a detection circuit due to aging, a transmission power detection circuit described in Japanese Unexamined Patent Application Publication No. 2006-13753 is proposed, for example. The details of each of the documents mentioned above will be described later with reference to FIG. 9(A) and FIG. 9(B).